Mammalian Ste20-like protein kinase 3 mediates trophoblast apoptosis in spontaneous delivery

The placenta is essential in transferring gases and nutrients from the mother to the developing fetus. Trophoblast apoptosis may cause labor or other pregnancy-related disorders. This study demonstrated the essential role of Mst3, a human Ste20-like protein kinase, in the oxidative stress-induced apoptosis of trophoblasts of term placenta in normal spontaneous delivery. Oxidative stress, but not hormones released during labor such as prostaglandin E1, oxytocin or angiotensin II, induces the expression of Mst3 and apoptosis of human term placenta after elective Cesarean section without labor pain. The role of Mst3 in oxidative stress-induced apoptosis was further demonstrated in the 3A-sub-E, a human trophoblast cell line. The H2O2-induced apoptosis of 3A-sub-E cells was largely suppressed by overexpressed Mst3KR, the kinase-dead mutant or by selective knockdown of endogenous Mst3. Further studies showed that Jun N-terminal kinase (JNK) may participate in the signaling pathway of H2O2-induced apoptosis by mediating the level of Mst3. Subsequently, caspase 3 and other downstream apoptotic components may be activated by Mst3 and trigger the apoptotic process in human trophoblasts.